JP2006186540A - Incoming direction estimation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an incoming direction estimation apparatus in which a miniaturization and a cost reduction are possible, reliability and durability are excellent, and no calibration by no skillful technology, etc. are required. <P>SOLUTION: In the incoming direction estimation apparatus, a joint switching means 20 controls the reactance set of varactor diodes 11-16 by control voltage sets CLV1-CLV6 so that an antenna element 7 and antenna elements 1-6 which element coupling may rotate the ambients of the antenna element 7. An array antenna 10 receives a received signal when the antenna element 7 and the antenna elements 1-6 which perform element coupling rotation ambients of the antenna element 7. A frequency shift detection means 40 detects the frequency shift spectrum of the incoming wave based on the received signal received from the antenna element 7 through a booster 30. A direction estimation means 50 presumes an angle in which the frequency shift spectrum performs a zero cross to be the incoming direction of the incoming wave. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an arrival direction estimation apparatus that estimates an arrival direction of an incoming wave.

  Conventionally, as a direction detection device using the Doppler effect, a plurality of antenna elements are arranged at equal intervals on a circumference of a horizontal plane, and among the plurality of antenna elements, an antenna element connected to a receiving unit is used by using an antenna switch. What is switched is known (Non-Patent Document 1).

  In such a conventional technique, the antenna switching device sequentially switches the antenna elements connected to the receiving unit at equal phase intervals along the circumference, so that the receiving position is at a constant velocity (constant velocity circular motion) on the circumference. Moving.

On the other hand, the transmitter transmits a CW wave that vibrates at a constant frequency. At this time, if the interval between adjacent antenna elements is sufficiently close to the wavelength of the CW wave (for example, half a wavelength or less), the frequency of the incoming wave input to the receiving unit is substantially periodic due to the Doppler effect. Change (a Doppler frequency shift occurs), and a frequency-modulated wave (FM wave) corresponding to the switching speed of the antenna element is formed. Since the phase of the signal obtained by demodulating the FM wave depends on the arrival direction of the CW wave, the arrival direction of the incoming wave can be estimated based on the phase of the FM wave demodulated signal.
The Institute of Electronics, Information and Communication Engineers, “Antenna Engineering Handbook”, Ohmsha, October 1980, p. 364-365

  However, in the direction finder using the Doppler effect according to the prior art, an antenna switch for switching and connecting each antenna element to the receiving unit is required, and transmission for connecting each antenna element to the antenna switch. The number of paths required was the same as the number of antenna elements. For this reason, there is a problem that the structure is complicated and the apparatus tends to be large, the manufacturing cost is high, and the power consumption is large.

  In addition, since the antenna switching unit switches and connects each antenna element and the receiving unit, the antenna switching unit is liable to fail due to wear of mechanical contacts and the like, and the reliability and durability tend to be inferior.

  Furthermore, in order for the time change of the Doppler frequency shift accompanying the antenna switching to follow a sine wave, the transmission paths between the antenna elements and the antenna switch have to be precisely aligned with each other. For this reason, it is necessary to finely adjust the length of the cable forming the transmission path for each cable, and there is a problem that it takes a long time to adjust the cable and requires a skilled technique.

  Therefore, the present invention has been made to solve such a problem, and its purpose is to be able to reduce the size and cost, and to be excellent in reliability and durability, and adjustment by skilled techniques is unnecessary. Is to provide a simple arrival direction estimation device.

  According to this invention, the arrival direction estimation apparatus includes an array antenna, a coupling switching unit, a frequency shift detection unit, and a direction estimation unit. The array antenna includes a feeding element and n (n is a plurality) parasitic elements arranged around the feeding element. The coupling switching unit changes the impedance of at least one of the n impedance elements loaded on the n parasitic elements to switch the parasitic elements that are coupled to the power feeding elements. The frequency deviation detecting means is configured to receive a reception signal of an incoming wave received by the array antenna from the feed element when the parasitic element coupled with the feed element is sequentially switched at a predetermined speed so as to rotate around the feed element. The frequency shift spectrum of the incoming wave is detected based on the received signal received. The direction estimating means detects an angle at which the frequency deviation spectrum detected by the frequency deviation detecting means intersects a reference line indicating that the frequency deviation is zero, and the detected angle is used as the arrival direction of the incoming wave. Estimated.

  Preferably, the direction estimating means detects an angle at which the frequency shift spectrum intersects the reference line when the frequency shift is switched from a positive value to a negative value, and the detected angle is set as the arrival direction of the incoming wave. presume.

  Preferably, the direction estimating means detects an angle at which the frequency shift spectrum intersects the reference line when the frequency shift is switched from a negative value to a positive value, and the detected angle is set as the arrival direction of the incoming wave. presume.

  Preferably, the coupling switching unit is configured such that all of the n parasitic elements are coupled to the feeding element, and the parasitic element mainly coupled to the feeding element rotates around the feeding element at a predetermined speed. The element coupling between the feed element and the n parasitic elements is switched.

  Preferably, the coupling switching unit is configured such that some of the n parasitic elements are coupled to the feeding element, and the parasitic element coupled to the feeding element has a predetermined speed around the feeding element. The element coupling between the feeding element and the n parasitic elements is switched so as to rotate at the same time.

Preferably, the arrival direction estimation device further includes a band rejection filter. The band rejection filter suppresses the center frequency component of the incoming wave from the received signal, and outputs the received signal in which the center frequency component of the incoming wave is suppressed to the frequency shift detecting means. And the space | interval of a feed element and the said parasitic element is set to the space | interval which suppresses the center frequency component of an incoming wave. The frequency shift detection means detects the frequency shift spectrum based on the received signal output from the band rejection filter. Preferably, the n parasitic elements are arranged in a substantially circular shape around the feed element. The

  Preferably, the impedance element is a variable capacitance element.

  In the direction-of-arrival estimation apparatus according to the present invention, the frequency deviation of the incoming wave is based on the received signal received by the array antenna when the parasitic element coupled to the feed element is sequentially switched to rotate around the feed element. The shift spectrum is detected, and the angle at which the detected frequency shift spectrum crosses zero is estimated as the arrival direction of the incoming wave. Then, switching of the parasitic element coupled to the feeder element is performed by changing the impedance of the impedance element loaded on the parasitic element.

  Therefore, according to the present invention, the parasitic element coupled with the feeding element can be switched electrically, and a failure due to the switching of the mechanical parasitic element can be prevented. As a result, reliability and durability can be improved.

  In addition, when a parasitic element coupled with a feeding element is sequentially switched so as to rotate around the feeding element, the received signal is detected only from the feeding element that is the central element. It is not necessary to provide and adjust each parasitic element.

  Furthermore, if the impedance switching wiring is connected to the impedance element, the impedance of the impedance element can be changed, so that adjustment by skilled techniques can be eliminated.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic diagram showing the configuration of an arrival direction estimation apparatus according to an embodiment of the present invention. Referring to FIG. 1, arrival direction estimation apparatus 100 includes array antenna 10, coupling switching unit 20, amplifier 30, frequency shift detection unit 40, and direction estimation unit 50.

  Array antenna 10 includes antenna elements 1 to 7, a ground plate 8, and varactor diodes 11 to 16. The ground plate 8 is made of a circular conductive metal material, and is arranged substantially parallel to the xy plane of xyz orthogonal coordinates including the x axis, the y axis, and the z axis. The antenna elements 1 to 7 are arranged substantially perpendicular to the ground plate 8 along the z-axis in xyz orthogonal coordinates. In this case, the antenna element 7 is disposed at the origin O of the xy coordinates.

  FIG. 2 is a plan layout view of the antenna elements 1 to 7 in the xy plane shown in FIG. Referring to FIG. 2, antenna elements 1 to 6 are arranged in a circle on a circumference CRC having a radius r with antenna element 7 as the center. That is, the antenna elements 1 to 6 are arranged in a circle around the antenna element 7. In this case, the antenna elements 1 to 6 are arranged at equal intervals. Further, when the wavelength of the radio wave transmitted and received by the array antenna 10 is λ, the radius r is set to 0.25λ or 0.383λ.

  Referring to FIG. 1 again, antenna elements 1 to 6 are parasitic elements, and antenna element 7 is a feed element. Varactor diodes 11-16 are connected between antenna elements 1-6 and the ground node, respectively. Thereby, the varactor diodes 11 to 16 which are variable capacitance elements are loaded on the antenna elements 1 to 6 which are parasitic elements, respectively.

  As described above, the array antenna 10 includes seven antenna elements, each including six parasitic elements (antenna elements 1 to 6) and one feeding element (antenna element 7), with a circular shape centering on the feeding element. It consists of the structure arranged in.

  The coupling switching means 20 supplies the control voltage sets CVL1 to CVL6 to the varactor diodes 11 to 16, and switches the coupling between the antenna elements 1 to 6 that are parasitic elements and the antenna element 7 that is a feeding element. The capacitances (reactance values) of the varactor diodes 11 to 16 are changed by the control voltages CVL1 to CVL6, respectively. The coupling switching means 20 determines the voltage values of the control voltages CVL1 to CVL6 so that the reactance values in the varactor diodes 11 to 16 become “hi” (maximum value) or “lo” (minimum value). The sets CVL1 to CVL6 are supplied to the varactor diodes 11 to 16. For example, the coupling switching means 20 supplies the control voltages CLV1 to CLV6 of 20V to the varactor diodes 11 to 16, respectively, sets the reactance value in the varactor diodes 11 to 16 to "hi", and controls the control voltage CLV1 of 0V. CLV6 is supplied to varactor diodes 11-16, respectively, and the reactance value in varactor diodes 11-16 is set to "lo".

In this case, coupling switching means 20, the reactance value _x m1 _{~x m6} reactance set _{x m} varactor control voltage set CVL1~CVL6 to vary as shown in Table 1 diodes in the varactor diodes 11 to 16 11 to 16 To supply.

When the reactance value x _m1 is “lo” and the reactance values x _{m2 to} x _m6 are “hi” (m = 1), the array antenna 10 has a beam pattern BPM1 having directivity in the direction of 0 degrees. . In this case, the antenna element 1 is strongly coupled to the antenna element 7, and the antenna elements 2 to 6 are weakly coupled to the antenna element 7. Note that the direction from the antenna element 7 (feeding element) to the antenna element 1 (parasitic element) is a 0 degree direction (see FIG. 2).

When the reactance value x _m2 is “lo” and the reactance values x _m1 , x _{m3 to} x _m6 are “hi” (m = 2), the array antenna 10 has directivity in the direction of 60 degrees. It has a beam pattern BPM2. In this case, the antenna element 2 is strongly coupled to the antenna element 7, and the antenna elements 1, 3 to 6 are weakly coupled to the antenna element 7.

Similarly, when the reactance values x _{m3 to} x _m6 are “lo” and the other reactance values are “hi” (m = 3 to 6), the array antenna 10 is 120 degrees, respectively. , Beam patterns BPM3 to BPM6 having directivity in directions of 180 degrees, 240 degrees, and 300 degrees (see FIG. 2). In this case, each of the antenna elements 3 to 6 is strongly coupled to the antenna element 7, and the other antenna elements (the antenna elements other than the antenna elements 3 to 6 among the antenna elements 1 to 6) are the antenna element 7. Are weakly coupled.

As described above, the coupling switching unit 20 radiates the antenna element 7 (feeding element) and the radiation by changing the reactance values x _{m1 to} x _m6 of the varactor diodes 11 to 16 loaded on the antenna elements 1 to 6 which are parasitic elements. The antenna elements 1 to 6 (parasitic elements) to be coupled are switched, and the directivity of the array antenna 10 is switched.

  When estimating the direction of arrival of the incoming wave, the coupling switching means 20 is configured so that the parasitic element (at least one of the antenna elements 1 to 6) coupled to the antenna element 7 that is the feeding element passes around the antenna element 7. Control voltage sets CLV1 to CLV6 are supplied to varactor diodes 11 to 16 so as to rotate at a predetermined speed.

The coupling switching unit 20 includes a pulse generator 21, a reactance value table 22, and a variable reactance control device 23. The pulse generator 21 generates a pulse signal PLS with a constant period, and outputs the generated pulse signal PLS to the variable reactance control device 23. In this case, the pulse signal PLS is, for example, an angular frequency ω _r having a value obtained by multiplying the angular frequency ω ₀ (ω ₀ = 2π × 1 kHz) by the number n (n = 6) of parasitic elements (antenna elements 1 to 6). (Ω _r = 2π × 6 kHz).

  The reactance value table 22 stores reactance tables XTB1 to XTB3 shown in Tables 2 to 4.

  The variable reactance control device 23 generates control voltage sets CLV1 to CLV6 according to any of the reactance tables XTB1 to XTB3 shown in Tables 2 to 4, and receives the generated control voltage sets CLV1 to CLV6 from the pulse generator 21. The varactor diodes 11 to 16 are supplied in synchronization with the pulse signal PLS.

For example, when the variable reactance control device 23 generates the control voltage sets CLV1 to CLV6 according to the reactance table XTB1 shown in Table 2, first, the reactance value x _m1 of the varactor diode 11 is set to 0Ω according to the reactance set XS11 of the reactance table XTB1. becomes, and the reactance value _x m @ 2 _{~x m6} varactor diodes 12 to 16 generates a control voltage set CLV1~CLV6 to be 457.5Omu, a control voltage CLV1~CLV6 that the generated to the varactor diodes 11 to 16 Supply.

Next, the variable reactance control device 23 sets the reactance value x _m2 of the varactor diode 12 to 0Ω according to the reactance set XS12 of the reactance table XTB1, and reactance values x _{m1, m3 to} x _{3 of} the varactor diodes 11 and 13 to 16 Control voltage sets CLV1 to CLV6 are generated so that _m6 is 457.5Ω, and the generated control voltages CLV1 to CLV6 are supplied to the varactor diodes 11 to 16.

  Thereafter, similarly, the variable reactance control device 23 generates control voltage sets CLV1 to CLV6 according to the reactance sets XS13 to XS16 of the reactance table XTB1, and supplies the generated control voltage sets CLV1 to CLV6 to the varactor diodes 11 to 16. To do.

In this case, the variable reactance control device 23 sequentially supplies the control voltage sets CLV1 to CLV6 generated according to the reactance sets XS11 to XS16 to the varactor diodes 11 to 16 in synchronization with the pulse signal PLS. That is, the variable reactance control device 23 controls the reactance values x _{m1 to} x _m6 of the varactor diodes 11 to 16 to be sequentially switched at the speed of the angular frequency ω _r of the pulse signal PLS according to the reactance set XS11 to XS16 of the reactance table XTB1. Voltage sets CLV1 to CLV6 are supplied to varactor diodes 11 to 16.

  The amplifier 30 amplifies the reception signal (consisting of a high-frequency current) output from the antenna element 7 (feeding element) of the array antenna 10 and outputs the amplified reception signal to the frequency shift detection means 40. The frequency shift detection means 40 receives the received signal from the amplifier 30 and detects the frequency shift spectrum of the incoming wave based on the received signal by a method described later, and the detected frequency shift spectrum is detected. It outputs to the direction estimation means 50.

  The direction estimation unit 50 detects an angle at which the frequency shift spectrum from the frequency shift detection unit 40 intersects a reference line indicating that the frequency shift is zero, and uses the detected angle as the arrival direction of the incoming wave. Estimated.

In the present invention, the principle of estimating the direction of arrival will be described. The antenna element 7 that is a feeding element receives a carrier wave (for example, a wave having a frequency of 200 MHz) Sa1 transmitted from a transmitter P (not shown). In this case, since the varactor diodes 11 to 16 loaded on the antenna elements 1 to 6 which are parasitic elements are respectively set to reactance values x _{m1 to} x _m6 by the coupling switching means 20, the plurality of antenna elements 1 ˜6, at least one antenna element is radiatively coupled to the antenna element 7, thereby inducing a high-frequency current in at least one antenna element.

In addition, since the reactance values x _{m1 to} x _m6 of the varactor diodes 11 to 16 are cyclically changed, the antenna element that is radiatively coupled with the antenna element 7 moves cyclically on the circumference CRC.

  In general, when the transmitter P that radiates an electromagnetic wave having an angular frequency ω is stationary and the receiver Q moves at a velocity v (vector), the angular frequency of the received wave at the receiver Q is a frequency deviation due to the Doppler effect. Receive a move. When the magnitude of the frequency shift at this time is Δω, the frequency shift Δω is expressed by the following equation.

Δω = − (<v> · <e _PQ >) ω / c (1)
In the expression (1), the notation <A> represents the vector A. A vector <e _PQ > is a unit vector from the transmitter P to the receiver Q, and c is the speed of light. Further, a · b represents a scalar product of the vector a and the vector b.

FIG. 3 is a plan view showing array antenna 10 and transmitter P shown in FIG. Referring to FIG. 3, when it is considered that six antenna elements 1 to 6 are arranged in a sufficiently dense state on a circumferential CRC having a radius r, array antenna 10 has a feeding element (antenna element 7). The parasitic elements that are radiatively coupled to each other are sequentially switched in the order of the six antenna elements 1 to 6 arranged on the circumferential CRC to receive the incoming wave from the transmitter P. Therefore, it can be considered that the array antenna 10 (receiver Q) receives an incoming wave from the transmitter P while smoothly moving on the circumference CRC having the radius r. In this case, the parasitic element for emitting coupled to the antenna element 7 is a feed element (at least one antenna element of the antenna element 1-6) is moved on the circumference CRC at the angular frequency omega _R by coupling switching means 20 It is done.

  On the other hand, the transmitter P is assumed to be sufficiently separated from the diameter 2r of the circumference CRC where the antenna elements 1 to 6 are arranged. Further, as shown in FIG. 3, in addition to the orthogonal coordinates (x, y) described above, polar coordinates (R, θ) having the arrangement position of the antenna element 7 as the origin O are set. At time t = 0, the parasitic element (one antenna element that is most strongly radiatively coupled to the antenna element 7 among the antenna elements 1 to 6) that is radiatively coupled to the feeding element (antenna element 7) is θ = π. It is assumed that the transmitter P is arranged in the direction of θ = α.

  Then, the speed <v> of one parasitic element that is radiatively coupled to the feeding element (antenna element 7) is expressed by the following expression in the orthogonal coordinate system.

_{<V> = (rω r sinω} r t, -rω r cosω r t) xy ··· (2)
Note that the subscript xy in Expression (2) indicates that the expression is in an orthogonal coordinate system. The unit vector <e _PQ > from the transmitter P to the receiver Q is expressed by the following equation from FIG.

<E _PQ > = (− cos α, −sin α) _xy (3)
Then, when Expressions (2) and (3) are substituted into Expression (1), the magnitude of the angular frequency shift Δω of the received wave at the receiver Q is expressed by the following expression.

Δω = rω _r ω sin (ω _r t−α) / c (4)
From Expression (4), the frequency shift Δω of the reception frequency due to the parasitic element that is radiatively coupled to the feeding element (antenna element 7) depends on the direction α of the transmitter P.

  FIG. 4 is a schematic diagram showing an incoming wave arriving at array antenna 10 shown in FIG. The incoming wave (carrier wave Sa1) is assumed to arrive from the direction of the antenna element 1. The parasitic element (any one of the antenna elements 1 to 6) that is most strongly radiatively coupled to the feeding element (antenna element 7) rotates counterclockwise at a speed <v> on the circumference CRC.

Then, the parasitic element (any one of the antenna elements 1 to 6) that is most strongly radiatively coupled to the feeding element (antenna element 7) is sequentially switched from antenna element 1 → antenna element 2 → antenna element 3 → antenna element 4. The array antenna 10 receives the incoming wave Sa1 while moving away from the incoming wave Sa1 at a velocity <v>. As a result, the array antenna 10, an FM wave Sa21 having a low angular frequency omega _L than the angular frequency omega of the incoming wave Sa1 by the Doppler effect, receiving the reception signal Sa and incoming waves Sa1 are mixed. In this case, FM wave Sa21 is because it has a low angular frequency omega _L than the incoming waves Sa1, the period is longer than the incoming waves Sa1.

On the other hand, a period during which the parasitic element (any one of the antenna elements 1 to 6) that is most strongly radiatively coupled to the feeding element (antenna element 7) is sequentially switched from the antenna element 4 → the antenna element 5 → the antenna element 6 → the antenna element 1; The array antenna 10 receives the incoming wave Sa1 while approaching the incoming wave Sa1 at a velocity <v>. As a result, the array antenna 10, an FM wave Sa22 having a high angular frequency omega _H than the angular frequency omega of the incoming wave Sa1 by the Doppler effect, receiving the reception signal Sa and incoming waves Sa1 are mixed. In this case, FM wave Sa22 is because it has a high angular frequency omega _H than the incoming waves Sa1, the period is shorter than the incoming waves Sa1.

The frequency shift Δω is obtained by subtracting the angular frequency ω of the incoming wave Sa1 from the angular frequencies ω _L and ω _H of the FM waves Sa21 and Sa22. Therefore, the frequency shift Δω is such that the parasitic element (any one of the antenna elements 1 to 6) that is most strongly radiatively coupled to the feeding element (antenna element 7) is antenna element 1 → antenna element 2 → antenna element 3 → antenna element 4. During the period of switching sequentially, the parasitic element (any one of the antenna elements 1 to 6) that becomes a negative value and is most strongly radiatively coupled to the feeding element (antenna element 7) is the antenna element 4 → the antenna element 5 → the antenna element 6 → It becomes a positive value during the period of switching to the antenna element 1 sequentially. At the moment when the parasitic element (any one of the antenna elements 1 to 6) that is most strongly radiatively coupled to the feeding element (antenna element 7) is the antenna element 1 or the antenna element 4, the velocity <v> Since the component in the direction parallel to the arrival direction is zero, the frequency shift Δω is zero.

Then, when the angle frequency shift [Delta] [omega becomes zero when the frequency shift [Delta] [omega is switched from a positive value to a negative value omega _{r t} or frequency shift [Delta] [omega, is switched from a negative value to a positive value The angle ω _r t at which the frequency shift Δω becomes zero is the arrival direction of the incoming wave Sa1. This is also clear from the fact that in equation (4), when Δω = 0, ω _r t = α.

Note that the angle ω _r t at which the frequency deviation Δω becomes zero when the frequency deviation Δω is switched from a positive value to a negative value is set as the arrival direction of the incoming wave Sa1, or the frequency deviation Δω is a negative value. from either the frequency shift Δω when switching to a positive value and direction of arrival of the incoming wave Sa1 angle omega _{r t} becomes zero, when the control voltage set CLV1~CLV6 supplied to the varactor diodes 11 to 16 This is determined depending on the phase characteristic of the beam emitted from the array antenna 10.

That is, when the reactance of the varactor diodes 11 to 16 is sequentially switched according to the reactance table (any of the reactance tables XTB1 to XTB3), the frequency shift occurs when the phase of the beam radiated from the array antenna 10 changes from positive to negative. Δω is the frequency shift Δω when switching from a positive value to a negative value angle omega _{r t} becomes zero are determined to be the arrival direction of the incoming wave Sa1. Further, when the reactance of the varactor diodes 11 to 16 is sequentially switched according to the reactance table (any of the reactance tables XTB1 to XTB3), the frequency shift occurs when the phase of the beam radiated from the array antenna 10 changes from negative to positive. Δω is determined as negative frequency shift Δω when switching to a positive value to zero from the value angle ω _{r t} is the arrival direction of the incoming wave Sa1.

Therefore, in the present invention, when the reactance set of the varactor diodes 11 to 16 is sequentially switched according to the reactance table (any of the reactance tables XTB1 to XTB3), the phase of the beam radiated from the array antenna 10 changes from positive to negative. Or whether it changes from negative to positive is detected in advance. From the received signal Sa received by the array antenna 10 when the parasitic element (any one of the antenna elements 1 to 6) that is most strongly radiatively coupled to the feeding element (antenna element 7) is sequentially switched at the speed <v>. An FM wave Sa2 (consisting of FM waves Sa21 and Sa22) is extracted, and based on the extracted FM wave Sa2, the frequency shift Δω represented by the equation (4) is detected and plotted against the angle ω _r t The detected frequency shift spectrum is obtained, and furthermore, the angle ω _r t at which the frequency shift spectrum intersects the reference line where the frequency shift Δω becomes zero is detected. In this case, when the beam radiated from the array antenna 10 has a phase characteristic that changes from positive to negative, the angle ω _{r at} which the frequency deviation Δω becomes zero when the frequency deviation Δω is switched from a positive value to a negative value. When t is detected and the beam radiated from the array antenna 10 has a phase characteristic that changes from negative to positive, the angle at which the frequency deviation Δω becomes zero when the frequency deviation Δω switches from a negative value to a positive value ω _r t is detected.

  FIG. 5 is a diagram for explaining a frequency shift detection method in the frequency shift detection means 40 shown in FIG. FIG. 6 is a diagram showing the relationship between the phase difference and the azimuth angle. In FIG. 5, the vertical axis represents voltage, and the horizontal axis represents instantaneous angular frequency. In FIG. 6, the vertical axis represents the phase difference, and the horizontal axis represents the azimuth angle. Since the frequency is a time derivative of the phase, the frequency shift is expressed by a phase difference (hereinafter the same). The azimuth angle is defined as an angle θ shown in FIG.

Referring to FIG. 5, the relationship between the voltage and the instantaneous frequency is represented by a straight line k1. When the instantaneous frequency is the angular frequency omega _c of the incoming waves Sa1, so that the voltage is converted to 0V, and the relationship between the voltage and the instantaneous frequency are determined. The frequency shift detecting means 40 receives the received signal Sa from the amplifier 30, converts the instantaneous frequency of the received received signal Sa into a voltage according to the straight line k1, plots the converted voltage against the azimuth angle, and shifts the frequency. Obtain the transfer spectrum.

As described above, the array antenna 10 receives the reception signal Sa in which the incoming wave Sa1 and the FM wave Sa2 (FM waves Sa21 and Sa22) are mixed, and the incoming wave Sa1 has the angular frequency ω _c. The shift detection means 40 converts the instantaneous frequency of the incoming wave Sa1 of the received signal Sa into a voltage of 0V, and converts the instantaneous frequency of the FM wave Sa2 into a predetermined voltage according to the straight line k1.

The frequency shift detecting means 40 sequentially plots the converted voltage with respect to the angle ω _r t. As a result, as shown in FIG. 6, the frequency shift is plotted against the azimuth angle (= ω _r t). In this case, the curve connecting the peaks P1 to P14 shown in FIG. 6 is the frequency shift spectrum FHS.

  When the frequency shift detection unit 40 detects the frequency shift spectrum FHS, the frequency shift detection unit 40 outputs the detected frequency shift spectrum FHS to the direction estimation unit 50. Upon receiving the frequency shift spectrum FHS, the direction estimation means 50 estimates the azimuth angle at which the received frequency shift spectrum FHS crosses zero as the arrival direction of the incoming wave.

  FIG. 7 is a flowchart for explaining the operation of estimating the arrival direction of the incoming wave. When a series of operations is started, the phase characteristic of the beam emitted from the array antenna 10 when the reactances of the varactor diodes 11 to 16 are sequentially switched at a predetermined speed is detected (step S1).

Then, it is determined whether or not the phase characteristic detected in step S1 changes from positive to negative when the azimuth is changed in the range of 0 degrees to 360 degrees (step S2). When the phase characteristic detected in step S1 changes from positive to negative (in the case of “YES” in step S2), the frequency deviation Δω is zero when the frequency deviation Δω is switched from a positive value to a negative value. It is set to detect the angle ω _r t to become (step S3).

On the other hand, when the phase characteristic detected in step S1 changes from negative to positive (in the case of “NO” in step S2), the frequency shift when the frequency shift Δω is switched from a negative value to a positive value. It is set to detect the angle ω _r t at which Δω becomes zero (step S4).

  After step S3 or step S4, when the reactances of the varactor diodes 11 to 16 are sequentially switched at a predetermined speed, the array antenna 10 receives the received signal Sa (step S5), and the received received signal Sa is transmitted to the antenna. Output from the element 7 (feeding element) to the amplifier 30.

The amplifier 30 receives the received signal Sa from the array antenna 10, amplifies the received signal Sa, and outputs it to the frequency shift detecting means 40. The frequency shift detection means 40 detects the frequency shift Δω by the above-described method based on the received signal Sa, plots the detected frequency shift Δω against the angle ω _r t, and generates the frequency shift spectrum FHS. Is created (step S6). Then, the frequency shift detection means 40 outputs the created frequency shift spectrum FHS to the direction estimation means 50.

The direction estimation means 50 receives the frequency shift spectrum FHS and detects an angle ω _r t at which the received frequency shift spectrum FHS crosses zero. When steps S5 to S7 are executed after step S3, the direction estimation means 50 determines that the angle ω _r t at which the frequency deviation Δω becomes zero when the frequency deviation Δω is switched from a positive value to a negative value. And the detected angle ω _r t is estimated as the arrival direction of the incoming wave Sa1. In addition, when steps S5 to S7 are executed after step S4, the direction estimation means 50 determines that the angle ω at which the frequency shift Δω becomes zero when the frequency shift Δω is switched from a negative value to a positive value. detecting a _r t, it estimates the detected angle omega _r t and the arrival direction of the incoming wave Sa1 (step S7).

  Thereby, a series of operations are completed.

  As described above, in the arrival direction estimation device 100, at least one of the parasitic elements (at least one of the antenna elements 1 to 6) that is radiatively coupled to the feed element (antenna element 7) by electrically switching the reactances of the varactor diodes 11 to 16. Are switched sequentially, and the frequency shift spectrum FHS of the incoming wave Sa1 is detected on the basis of the received signal Sa (consisting of the incoming wave Sa1 and the FM wave Sa2) received by the array antenna 10 at that time. The angle at which the frequency shift spectrum FHS is zero-crossed is estimated as the arrival direction of the incoming wave Sa1.

  Therefore, according to the present invention, the parasitic elements (antenna elements 1 to 6) coupled to the feeding element (antenna element 7) can be switched electrically, and failure due to the switching of the mechanical parasitic elements can be prevented. Can be prevented. As a result, reliability and durability can be improved.

  In addition, when a parasitic element coupled with a feeding element is sequentially switched so as to rotate around the feeding element, the received signal is detected only from the feeding element that is the central element. It is not necessary to provide and adjust each parasitic element.

  Furthermore, if the wiring for switching the reactance is connected to the varactor diodes 11 to 16, the reactance of the varactor diodes 11 to 16 can be changed, so that adjustment by skilled techniques can be made unnecessary.

In the flowchart shown in FIG. 7, the angle at which the frequency deviation Δω becomes zero when the frequency deviation Δω is switched from a positive value to a negative value depending on whether or not the phase characteristic has changed from positive to negative. Although it was determined whether or not to estimate ω _r t as the arrival direction of the incoming wave Sa1 (see steps S2 to S4), the present invention is not limited to this, and the phase change rate changes from positive to negative The angle ω _r t at which the frequency shift Δω becomes zero when the frequency shift Δω is switched from a positive value to a negative value is estimated as the arrival direction of the incoming wave Sa1, and the phase change rate changes from negative to positive. When the frequency shift Δω changes, the angle ω _r t at which the frequency shift Δω becomes zero when the frequency shift Δω is switched from a negative value to a positive value may be estimated as the arrival direction of the incoming wave Sa1.

  The result of the simulation using the arrival direction estimation method described above will be described.

[Simulation 1]
FIG. 8 is a phase characteristic diagram of a beam when two antenna elements of the array antenna 10 shown in FIG. 1 are combined. In FIG. 8, the vertical axis represents the phase, and the horizontal axis represents the azimuth angle. The combination of two antenna elements refers to the combination of one antenna element of antenna elements 1 to 6 and antenna element 7.

In this case, the coupling switching means 20 sequentially switches the reactances x _{m1 to} x _m6 of the varactor diodes 11 to 16 according to the reactance sets XS11 to XS16 of the reactance table XTB1 shown in Table 2.

That is, the coupling switching means 20 first sets the reactance x _m1 of the varactor diode 11 to 0Ω according to the reactance set XS11, and sets all of the reactances x _{m2 to} x _m6 of the varactor diodes 12 to 16 to 457.5Ω. To do. Thereby, the antenna element 1 and the antenna element 7 are radiatively coupled, and the array antenna 10 radiates the beam BM1 from the antenna element 7 toward the antenna element 4.

Next, the coupling switching unit 20 sets the reactance x _m2 of the varactor diode 12 to 0Ω according to the reactance set XS12, and all the reactances x _m1 , x _{m3 to} x _m6 of the varactor diodes 11 and 13 to 457 are 457. Set to 5Ω. As a result, the antenna element 2 and the antenna element 7 are radiatively coupled, and the array antenna 10 radiates the beam BM1 from the antenna element 7 toward the antenna element 5.

Similarly, the coupling switching unit 20 sequentially sets the reactances x _{m3 to} x _m6 of the varactor diodes 13 to 16 to 0Ω according to the reactance sets XS13 to XS16, and the other varactor diodes x _m1 , x _m2 and x _{m4. ~x m6; x m1 ~x m3,} x m5, x m6; x m1 ~x m4, x m6; all reactance x m1 _{~x m5} sequentially set to 457.5Omu. As a result, the antenna element 7 is sequentially radiatively coupled to the antenna elements 3 to 6, and the array antenna 10 transmits the beam BM1 in the direction from the antenna element 7 to the antenna element 6, the direction from the antenna element 7 to the antenna element 1, and the antenna element 7 To antenna element 2 and antenna element 7 to antenna element 3 in this order.

  Thus, the coupling switching means 20 sequentially switches the reactances of the varactor diodes 11 to 16 to the reactances shown in Table 2 according to the reactance sets XS11 to XS16, so that the parasitic element that is radiatively coupled to the feed element (antenna element 7) is The elements are sequentially switched to elements 1 to 6, and the array antenna 10 emits a beam BM1 that rotates counterclockwise.

  The phase characteristic of the curve k2 shows the phase when the beam BM1 radiated from the array antenna 10 is rotated counterclockwise with respect to the azimuth angle. In this simulation, the distance between the antenna elements 1 to 6 and the antenna element 7 is 0.25λ, the frequency of the incoming wave Sa1 (that is, the center frequency) is 200 MHz, and the signal-to-noise ratio (SNR) is infinite ( ∞), and the true arrival direction of the incoming wave Sa1 was 0 degrees (direction from the antenna element 7 to the antenna element 1). The incoming wave Sa1 is referred to as a “center frequency component”.

  The phase characteristic varies in a range of about 40 to 80 degrees with respect to an azimuth angle in the range of 0 to 360 degrees, and has two local maximum points and two local minimum points. When the azimuth angle changes from 0 degrees to 60 degrees, the phase changes from about 40 degrees to about 70 degrees, and the phase change rate becomes positive. Further, when the azimuth angle changes from 60 degrees to 120 degrees, the phase changes from about 80 degrees to about 70 degrees, and the phase change rate becomes negative.

  FIG. 9 is a diagram showing the frequency dependence of the received power spectrum when the two antenna elements of the array antenna 10 shown in FIG. 1 are combined. In FIG. 9, the vertical axis represents the received power spectrum, and the horizontal axis represents the frequency. The received power spectrum has a component SS1 corresponding to the frequency (= 200 MHz) of the incoming wave Sa1 and components SS2 to SS6 corresponding to the frequency shift (FM wave Sa2).

  FIG. 10 is a diagram showing a frequency shift spectrum when two antenna elements of the array antenna 10 shown in FIG. 1 are combined. In FIG. 10, the vertical axis represents the phase difference (= frequency shift), and the horizontal axis represents the azimuth angle. FIG. 10 shows a frequency shift when the beam BM1 is rotated twice counterclockwise.

  As described above, since the phase change rate is positive in the range of 0 to 60 degrees and negative in the range of 60 to 120 degrees, the frequency shift is switched from a positive value to a negative value. The azimuth angle at which the frequency shift is zero should be estimated as the arrival direction of the incoming wave Sa1, but in the array antenna 10, when two antenna elements are radiatively coupled, the beam BM1 emitted by the array antenna 10 is As shown in FIG. 8, the direction of arrival of the incoming wave Sa1 is opposite to the direction indicated by the arrow. Therefore, the azimuth angle at which the frequency shift becomes zero when the frequency shift is switched from a negative value to a positive value is estimated as the arrival direction of the incoming wave Sa1.

  As a result, directions of 0 degrees and 180 degrees were estimated as directions of arrival from the results shown in FIG. Thus, the two arrival directions exist because the phase characteristic of the beam BM1 has two local maximum points and two local minimum points as shown in FIG.

  In this manner, in the array antenna 10 composed of the feeding element (antenna element 7) and the parasitic elements (antenna elements 1 to 6), two antenna elements (feeding element and one parasitic element) are radiatively coupled. In this case, the azimuth angle at which the frequency shift is zero can be estimated as the arrival direction of the incoming wave.

  FIG. 11 is a phase characteristic diagram of a beam in a two-element array antenna composed of two antenna elements. Array antenna 60 includes antenna elements 61 to 67 and a ground plate 68. The ground plate 68 is made of a circular conductive metal material. The antenna elements 61 to 67 are disposed substantially perpendicular to the ground plate 68 (in a direction perpendicular to the paper surface), and are disposed at positions corresponding to the positions of the antenna elements 1 to 7 of the array antenna 10, respectively. The distance r between the antenna elements 61 to 66 and the antenna element 67 is 0.25λ.

  By connecting the antenna element 67 to the antenna element 61 and feeding power to the connected antenna elements 61 and 67, a two-element array antenna is formed. Therefore, six antennas (not shown) are provided between the antenna elements 61 to 66 and the antenna element 67, and one antenna connected to the antenna element 67 is switched by sequentially switching the six switches. The element (any one of the antenna elements 61 to 66) can be switched. That is, the two-element array antenna can be rotated counterclockwise about the antenna element 67. When the antenna element 61 and the antenna element 67 are connected, the two-element array antenna radiates the beam BM2.

  The phase characteristic of the curve k3 shows the phase when the beam BM2 radiated from the two-element array antenna is rotated counterclockwise with respect to the azimuth angle. The conditions in this simulation are the same as the simulation conditions when the simulation results shown in FIGS.

  The phase characteristic varies in a range of about 20 degrees to 80 degrees with respect to an azimuth angle in the range of 0 degrees to 360 degrees, and has two local maximum points and two local minimum points. The phase change ratio is positive in the range of 0 to 60 degrees and negative in the range of 60 to 120 degrees. This result is the same as the result shown in FIG.

  FIG. 12 is a diagram showing the frequency dependence of the received power spectrum in a two-element array antenna composed of two antenna elements. In FIG. 12, the vertical axis represents the received power spectrum, and the horizontal axis represents the frequency. The received power spectrum has a component SS7 corresponding to the frequency (= 200 MHz) of the incoming wave Sa1 and components SS8 to SS12 corresponding to the frequency shift (FM wave Sa2). This result is the same as the result shown in FIG.

  FIG. 13 is a diagram showing a frequency shift spectrum in a two-element array antenna composed of two antenna elements. In FIG. 13, the vertical axis represents the phase difference (= frequency shift), and the horizontal axis represents the azimuth angle. FIG. 13 shows a frequency shift when the beam BM1 is rotated twice counterclockwise.

  When the beam BM2 radiated by the two-element array antenna is rotated counterclockwise, the beam BM2 radiated by the array antenna 60 is opposite to the arrival direction (indicated by the arrow) of the incoming wave Sa1, as shown in FIG. It is. Therefore, the azimuth angle at which the frequency shift becomes zero when the frequency shift is switched from a negative value to a positive value is estimated as the arrival direction of the incoming wave Sa1.

  As a result, directions of 0 degrees and 180 degrees were estimated as the arrival directions of the incoming wave Sa1 from the results shown in FIG. This result is the same as the result shown in FIG.

  As described above, in array antenna 10, one parasitic element (any one of antenna elements 1 to 6) that radiates and couples to the feed element (antenna element 7) is rotated counterclockwise to arrive the incoming wave Sa1. The result of estimating the direction is the same as the result of estimating the arrival direction of the incoming wave Sa1 by rotating the two-element array antenna counterclockwise.

  Therefore, in the array antenna 10, the frequency deviation of the received signal Sa when one parasitic element (any one of the antenna elements 1 to 6) radiatively coupled with the feeding element (antenna element 7) is rotated counterclockwise. It was found that the arrival direction of the incoming wave Sa1 can be estimated by detecting the shift.

[Simulation 2]
FIG. 14 is a phase characteristic diagram of the beam when the distance between the feeding element and the parasitic element in the array antenna 10 shown in FIG. FIG. 15 is a diagram showing the frequency dependence of the received power spectrum when the distance between the feeding element and the parasitic element in the array antenna 10 shown in FIG. Further, FIG. 16 is a diagram showing a frequency shift spectrum when the distance between the feed element and the parasitic element in the array antenna 10 shown in FIG.

  The interval between the feeding element (antenna element 7) and the parasitic element (antenna elements 1 to 6) in the simulation 2 is 0.383λ. Moreover, the simulation conditions in the simulation 2 are the same as the simulation conditions in the simulation 1.

  In FIG. 14, the vertical axis represents the phase, and the horizontal axis represents the azimuth angle. A phase characteristic when the parasitic element (any one of the antenna elements 1 to 6) radiatively coupled to the feeding element (antenna element 7) is sequentially switched according to the reactance set XS11 to XS16 is indicated by a curve k4. The phase of the beam BM1 changes in the range of about 40 degrees to 90 degrees with respect to the azimuth angle in the range of 0 to 360 degrees, and has two local maximum points and two local minimum points. The phase change ratio is positive in the range of 0 to 60 degrees and negative in the range of 60 to 120 degrees. This result is almost the same as the result shown in FIG.

  In FIG. 15, the vertical axis represents the received power spectrum, and the horizontal axis represents the azimuth angle. The received power spectrum includes a component SS13 corresponding to the frequency (= 200 MHz) of the incoming wave Sa1 and components SS14 to SS18 corresponding to the frequency shift (FM wave Sa2). This result is almost the same as the result shown in FIG.

  In FIG. 16, the vertical axis represents a phase difference (= frequency shift), and the horizontal axis represents an azimuth angle. FIG. 16 shows a frequency shift when the beam BM1 is rotated twice counterclockwise. As described above, since the phase change rate changes from positive to negative, the azimuth angle at which the frequency shift becomes zero when the frequency shift is switched from a positive value to a negative value is the arrival direction of the incoming wave Sa1. However, since the beam BM1 is directed in the opposite direction to the arrival direction of the incoming wave Sa1 (see FIG. 8), the frequency deviation is changed when the frequency deviation is switched from a negative value to a positive value. The azimuth angle at which the shift is zero is estimated as the arrival direction of the incoming wave Sa1. As a result, the direction of 0 degree was estimated as the arrival direction of the incoming wave Sa1.

  FIG. 17 is a diagram illustrating the frequency dependence of the received power spectrum when the frequency component of the incoming wave Sa1 is removed. In FIG. 17, the vertical axis represents the received power spectrum, and the horizontal axis represents the frequency. The received power spectrum does not have a frequency component corresponding to the incoming wave Sa1, but has components SS19 to SS23 corresponding to the frequency shift (FM wave Sa2).

  FIG. 18 is a diagram showing a frequency shift spectrum when the frequency component of the incoming wave Sa1 is removed. In FIG. 18, the vertical axis represents a phase difference (= frequency shift), and the horizontal axis represents an azimuth angle. From the results shown in FIG. 18, it was estimated that the azimuth angle of 0 degrees at which the frequency shift becomes zero when the frequency shift is switched from a positive value to a negative value is the arrival direction of the incoming wave Sa1.

  Thus, when two antenna elements of the array antenna 10 are radiatively coupled, the frequency shift of the incoming wave Sa1 is suppressed from a positive value to a negative value by suppressing the frequency component (= center frequency component) of the incoming wave Sa1. It can be estimated that the azimuth angle at which the frequency shift becomes zero when switching to is the arrival direction of the incoming wave Sa1.

  Therefore, the arrival direction estimation apparatus 100 suppresses the frequency component (= center frequency component) of the arrival wave Sa1 when estimating the arrival direction of the arrival wave Sa1 by radiating and coupling two antenna elements of the array antenna 10. A bandstop filter is included between the amplifier 30 and the frequency shift detector 40.

  FIG. 19 is a diagram illustrating the frequency dependence of the received power spectrum when an antenna without inter-element coupling is used. The antenna 70 includes antenna elements 71 to 77 and a ground plate 78. The ground plate 78 is made of a circular conductive metal material. The antenna elements 71 to 77 are arranged substantially perpendicular to the ground plate 78 (direction perpendicular to the paper surface), and are arranged at positions corresponding to the positions of the antenna elements 1 to 7 of the array antenna 10, respectively. The distance r between the antenna elements 71 to 76 and the antenna element 77 is 0.25λ.

  In the antenna 70, each of the antenna elements 71 to 76 arranged around the antenna element 77 can receive the reception signal Sa independently, and the antenna element 77 arranged in the center can also receive the reception signal Sa independently. It is an antenna. That is, the antenna 70 is an antenna in which each of the antenna elements 71 to 77 independently receives the reception signal Sa and outputs the reception signal Sa from each of the antenna elements 71 to 77.

  On the other hand, the array antenna 10 shown in FIG. 1 receives at least one antenna element from the antenna elements 1 to 6 and the antenna element 7 to receive the received signal Sa and outputs the received signal Sa from the antenna element 7. It is.

  When a received signal is received by any one of the antenna elements 71 to 76 while sequentially switching the antenna that receives the received signal among the antenna elements 71 to 76 without radiating and coupling the antenna elements 71 to 76 and the antenna element 77. FIG. 19 shows the frequency dependence of the received power spectrum.

  The received power spectrum has a component SS24 corresponding to the frequency of the incoming wave Sa1, and components SS25 to SS29 corresponding to the frequency shift (FM wave Sa2).

  FIG. 20 is a diagram showing a frequency shift spectrum when an antenna without inter-element coupling is used. In FIG. 20, the vertical axis represents the phase difference (= frequency shift), and the horizontal axis represents the azimuth angle. From the results shown in FIG. 20, it was estimated that the azimuth angle of 0 degree at which the frequency shift becomes zero when the frequency shift is switched from a positive value to a negative value is the arrival direction of the incoming wave Sa1.

  Thus, the frequency deviation is detected using the antenna 70 having the same arrangement as the antenna elements 1 to 7 of the array antenna 10 and having no inter-element coupling, and the detected frequency deviation is determined from a positive value. By detecting the azimuth angle at which the frequency shift is zero when switching to a negative value, the arrival direction of the incoming wave Sa1 can be estimated.

  FIG. 21 is a diagram showing the frequency dependence of the received power spectrum when the distance between antenna elements is widened in an antenna having no inter-element coupling. In FIG. 21, the vertical axis represents the received power spectrum, and the horizontal axis represents the frequency. In FIG. 21, the distance r between the antenna elements 71 to 76 of the antenna 70 and the antenna element 77 is set to 0.383λ.

  The received power spectrum does not have a component corresponding to the frequency (= 200 MHz) of the incoming wave Sa1, but has components SS30 to SS34 corresponding to the frequency shift (FM wave Sa2). In this way, by setting the interval r between the antenna elements 71 to 76 and the antenna element 77 to 0.383λ, the component corresponding to the frequency (= 200 MHz) of the incoming wave Sa1 is removed, and the frequency shift (FM wave) Only the components SS30 to SS34 corresponding to Sa2) can be detected.

  Of the components SS30 to SS34 corresponding to the frequency shift, the components SS32 to SS34 are larger than when the distance r between the antenna elements 71 to 76 and the antenna element 77 is 0.25λ (see FIG. 19). .

  FIG. 22 is a diagram showing a frequency shift spectrum when an antenna element interval is widened in an antenna having no inter-element coupling. In FIG. 22, the vertical axis represents the phase difference (= frequency shift), and the horizontal axis represents the azimuth angle. The frequency deviation shown in FIG. 22 is larger than the frequency deviation shown in FIG. Thus, a larger frequency shift can be detected by removing the component corresponding to the frequency (= 200 MHz) of the incoming wave Sa1.

  From the results shown in FIG. 22, it was estimated that the azimuth angle of 0 degrees at which the frequency shift becomes zero when the frequency shift is switched from a positive value to a negative value is the arrival direction of the incoming wave Sa1.

  In this way, by setting the distance r between the antenna elements 71 to 76 and the antenna element 77 to 0.383λ, a component corresponding to the frequency (= 200 MHz) of the incoming wave Sa1 can be removed, and a larger frequency shift can be achieved. Since it can be detected, the arrival direction of the incoming wave Sa1 can be accurately estimated.

  The array antenna 10 receives the reception signal Sa in which the incoming wave Sa1 and the FM wave Sa2 (consisting of the FM waves Sa21 and Sa22) are mixed by a single feeding element (antenna element 7). Even if the interval r to the antenna element 7 is set to 0.383λ, as shown in FIG. 15, the array antenna 10 has a component SS13 corresponding to the frequency (= 200 MHz) of the incoming wave Sa1 and a frequency shift (FM). The components SS14 to SS18 corresponding to the wave Sa2) are detected.

  Therefore, by passing the received signal Sa (consisting of the incoming wave Sa1 and the FM wave Sa2) received by the array antenna 10 through a band rejection filter, the component SS13 corresponding to the frequency (= 200 MHz) of the incoming wave Sa1 is removed. The components SS19 to SS23 corresponding to the frequency shift (FM wave Sa2) become large (see FIG. 17). As a result, as shown in FIG. 18, a larger frequency shift can be detected, and the arrival direction of the incoming wave Sa1 can be accurately estimated. The frequency shift shown in FIG. 18 has almost the same magnitude as the frequency shift shown in FIG.

  Therefore, when the arrival direction of the incoming wave Sa1 is estimated by radiatively coupling two antenna elements of the array antenna 10, a band rejection filter for removing the frequency (= 200 MHz) of the incoming wave Sa1 is provided. The distance r between 71 to 76 and the antenna element 77 is set to 0.383λ, and the arrival direction of the incoming wave Sa1 is estimated with the same accuracy as the antenna 70 that does not detect the component corresponding to the frequency (= 200 MHz) of the incoming wave Sa1. it can.

  In this case, the arrival direction estimation apparatus 100 sets the interval between the antenna elements 1 to 6 and the antenna element 7 to an interval that suppresses the component of the incoming wave Sa1 whose frequency shift is substantially zero in the antenna 70 having no inter-element coupling. And has a configuration including a band rejection filter between the amplifier 30 and the frequency shift detection means 40.

[Simulation 3]
FIG. 23 is a phase characteristic diagram of a beam when all the antenna elements of the array antenna 10 shown in FIG. 1 are combined. In FIG. 23, the vertical axis represents the phase, and the horizontal axis represents the azimuth angle. The coupling of all antenna elements means that the antenna elements 1 to 6 and the antenna element 7 are coupled. However, not all of the antenna elements 1 to 6 are coupled to the antenna element 7 at the same ratio, and any one of the antenna elements 1 to 6 is strongly coupled to the antenna element 7. These antenna elements are weakly coupled to the antenna element 7.

  The interval r between the antenna elements 1 to 6 and the antenna element 7 is 0.25λ, and the simulation conditions are the same as the simulation conditions of the simulation 1 described above.

In this case, the coupling switching means 20 sequentially switches the reactances x _{m1 to} x _m6 of the varactor diodes 11 to 16 according to the reactance sets XS21 to XS26 of the reactance table XTB2 shown in Table 3.

That is, the coupling switching means 20 first sets the reactance x _m1 of the varactor diode 11 to −90Ω according to the reactance set XS21, and sets all of the reactances x _{m2 to} x _m6 of the varactor diodes 12 to 16 to 30Ω. . Thereby, the antenna element 1 and the antenna element 7 are strongly radiatively coupled, and the antenna elements 2 to 6 and the antenna element 7 are weakly radiatively coupled.

Next, the coupling switching unit 20 sets the reactance x _m2 of the varactor diode 12 to −90Ω according to the reactance set XS22, and all the reactances x _m1 , x _{m3 to} x _m6 of the varactor diodes 11 and 13 to 16 are set. Set to 30Ω. Thereby, the antenna element 2 and the antenna element 7 are strongly radiatively coupled, and the antenna elements 1, 3 to 6 and the antenna element 7 are weakly radiatively coupled.

Hereinafter, similarly, the coupling switching unit 20 sequentially sets the reactances x _{m3 to} x _m6 of the varactor diodes 13 to 16 to −90Ω according to the reactance sets XS23 to XS26, and the other varactor diodes x _m1 , x _m2 , x _{m4 ~x m6; x m1 ~x m3} , x m5, x m6; x m1 ~x m4, x m6; all reactance x m1 _{~x m5} sequentially set to 30 [Omega. As a result, the antenna element 7 is successively strongly coupled to the antenna elements 3 to 6 and the antenna elements 1, 2, 4 to 6; 1 to 3, 5 and 6; 1 to 4 and 6; Sequentially weakly radiatively couple.

  As described above, the coupling switching means 20 sequentially switches the reactances of the varactor diodes 11 to 16 to the reactances shown in Table 3 according to the reactance sets XS21 to XS26. The antenna elements 1 to 6 are sequentially switched, and the array antenna 10 radiates a beam that rotates counterclockwise.

  The phase characteristic of the curve k5 shows the phase when the beam radiated from the array antenna 10 is rotated counterclockwise with respect to the azimuth angle.

  The phase characteristic varies in a range of about 15 degrees to about −220 degrees with respect to an azimuth angle in the range of 0 to 360 degrees, and has one local maximum point and one local minimum point. Then, when the azimuth angle changes from 0 degree to 60 degrees, the phase changes from positive to negative. In FIG. 23, the phase is shown to change in the range of about 140 degrees to about 180 degrees when the azimuth angle is in the range of about 100 degrees to about 260 degrees. In practice, the phase varies in the range of about -180 degrees to about -220 degrees in the range of azimuth angles of about 100 degrees to about 260 degrees.

  FIG. 24 is a diagram showing the frequency dependence of the received power spectrum when all the antenna elements of the array antenna 10 shown in FIG. 1 are combined. In FIG. 24, the vertical axis represents the received power spectrum, and the horizontal axis represents the frequency. The received power spectrum has a component SS35 corresponding to the frequency (= 200 MHz) of the incoming wave Sa1 and components SS36 to SS40 corresponding to the frequency shift (FM wave Sa2). The component SS35 corresponding to the frequency (= 200 MHz) of the incoming wave Sa1 is smaller than the components SS36 to SS40 corresponding to the frequency shift (FM wave Sa2).

  In this way, by radiatively coupling all the antenna elements 1 to 7 of the array antenna 10, the component SS35 corresponding to the frequency (= 200 MHz) of the incoming wave Sa1 is suppressed, and the frequency shift (FM wave Sa2) is supported. In some cases, the components SS36 to SS40 to be increased can be increased. Further, the beam directivity gain can be improved by radiatively coupling all of the antenna elements 1 to 7.

  FIG. 25 is a diagram showing a frequency shift spectrum when all the antenna elements of the array antenna 10 shown in FIG. 1 are combined. In FIG. 25, the vertical axis represents the phase difference (= frequency shift), and the horizontal axis represents the azimuth angle. FIG. 25 shows the frequency shift when the beam is rotated twice counterclockwise. The frequency shift shown in FIG. 25 is almost the same as the frequency shift shown in FIG.

  As described above, since the phase changes from positive to negative at an azimuth angle of 0 to 360 degrees, the azimuth angle at which the frequency deviation becomes zero when the frequency deviation is switched from a positive value to a negative value. The arrival direction of the incoming wave Sa1 is estimated.

  As a result, the direction of 0 degrees was estimated as the arrival direction of the incoming wave Sa1 from the result shown in FIG.

  In this way, in the array antenna 10 composed of the feeding element (antenna element 7) and the parasitic element (antenna elements 1 to 6), all of the antenna elements 1 to 7 are radiatively coupled, whereby the incoming wave Sa1 and the FM wave Even if the received signal Sa mixed with Sa2 is detected by one feeding element (antenna element 7), the component SS34 corresponding to the frequency (= 200 MHz) of the incoming wave Sa1 is suppressed, and the frequency shift (FM wave Sa2) is suppressed. ) Can be increased, and the arrival direction of the incoming wave Sa1 can be accurately estimated.

  In order to estimate the arrival direction of the incoming wave Sa1 by radiating and coupling all the antenna elements 1 to 7 of the array antenna 10, the following two conditions are necessary.

  (A) When the azimuth angle changes from 0 degrees to 360 degrees, there is one phase maximum and minimum.

  (B) When the azimuth angle changes by 60 degrees, the phase changes in a range smaller than 180 degrees.

  Therefore, if the above two conditions (A) and (B) are satisfied, the reactance set of the varactor diodes 11 to 16 is not limited to the reactance set XS21 to XS26 shown in Table 3, and all the antenna elements 1 to 7 are radiated. Other reactance sets may be combined.

[Simulation 4]
26 is a diagram showing directional gains at respective azimuth angles of the beam radiated from the array antenna 10 shown in FIG. In FIG. 26, the vertical axis represents the direction gain, and the horizontal axis represents the azimuth angle. A curve k6 indicates the directional gain at each azimuth angle of the beam emitted from the array antenna 10 when the reactance set of the varactor diodes 11 to 16 is set to the reactance set XS31 shown in Table 4.

  From the results shown in FIG. 26, when the reactance set of the varactor diodes 11 to 16 is set to the reactance set XS31, the array antenna 10 radiates a beam having directivity in two directions.

  FIG. 27 is a phase characteristic diagram of a beam emitted from the array antenna 10 shown in FIG. In FIG. 27, the vertical axis represents the phase, and the horizontal axis represents the azimuth angle. A curve k7 indicates the phase characteristic of the beam radiated from the array antenna 10 when the reactance set of the varactor diodes 11 to 16 is set to the reactance set XS31 shown in Table 4.

  From the result shown in FIG. 27, when the reactance set of the varactor diodes 11 to 16 is set to the reactance set XS31, the phase has two maximum points and two minimum points.

  FIG. 28 is a diagram showing a frequency shift spectrum when the reactance sets of the varactor diodes 11 to 16 are sequentially switched according to the reactance sets XS31 to XS36 shown in Table 4.

  In FIG. 28, the vertical axis represents the phase difference (= frequency shift), and the horizontal axis represents the central direction between the two beams, that is, the direction of the azimuth angle = 180 degrees. Further, the true arrival direction of the incoming wave Sa1 is a direction of 0 degrees (the direction indicated by the arrow in FIG. 28), and the signal-to-noise ratio (SNR) of the received signal Sa received by the array antenna 10 is infinite (∞ ).

  From the results shown in FIG. 28, it was estimated that the direction of 0 degree where the frequency shift becomes zero when the frequency shift is switched from a positive value to a negative value is the arrival direction of the incoming wave Sa1.

  FIG. 29 is a diagram showing another frequency shift spectrum when the reactance sets of the varactor diodes 11 to 16 are sequentially switched according to the reactance sets XS31 to XS36 shown in Table 4.

  In FIG. 29, the vertical axis represents the phase difference (= frequency shift), and the horizontal axis represents the central direction between the two beams. In addition, the true arrival direction of the incoming wave Sa1 is a 0 degree direction (the direction indicated by the arrow in FIG. 29), and the signal-to-noise ratio (SNR) of the received signal Sa received by the array antenna 10 is 20 dB. .

  From the result shown in FIG. 29, the direction of 0.2792 degrees and the direction of -0.9039 degrees at which the frequency deviation becomes zero when the frequency deviation is switched from a positive value to a negative value are arrival of the incoming wave Sa1. Estimated direction.

  As described above, when the noise increases, the estimated arrival direction slightly deviates from the true arrival direction, but the arrival direction of the incoming wave Sa1 can be accurately estimated by averaging several trials.

  FIG. 30 is a diagram showing still another frequency shift spectrum when the reactance sets of the varactor diodes 11 to 16 are sequentially switched according to the reactance sets XS31 to XS36 shown in Table 4.

  In FIG. 30, the vertical axis represents the phase difference (= frequency shift), and the horizontal axis represents the central direction between the two beams. The true arrival direction of the incoming wave Sa1 is a direction of 15 degrees (the direction indicated by the arrow in FIG. 30), and the signal-to-noise ratio (SNR) of the received signal Sa received by the array antenna 10 is infinite (∞ ).

  From the result shown in FIG. 30, it was estimated that the direction of 14.9628 degrees at which the frequency shift becomes zero when the frequency shift is switched from a positive value to a negative value is the arrival direction of the incoming wave Sa1.

  Thus, by sequentially switching the reactance set of the varactor diodes 11 to 16 according to the reactance table XTB3 shown in Table 4, the angle at which the frequency shift becomes zero when the frequency shift is switched from a positive value to a negative value. Can be estimated as the arrival direction of the incoming wave Sa1.

  As described above, the arrival direction of the incoming wave Sa1 can be accurately estimated even using a beam having two peaks.

  In the above description, the case where one of the antenna elements 1 to 6 is radiatively coupled to the antenna element 7 and the case where all of the antenna elements 1 to 6 are radiatively coupled to the antenna element 7 have been described. The present invention is not limited to this, and among the antenna elements 1 to 6, two antenna elements, three antenna elements, four antenna elements, and five antenna elements are radiatively coupled to the antenna element 7. Also good. That is, some parasitic elements of the six parasitic elements (antenna elements 1 to 6) may be radiatively coupled to the feeding element (antenna element 7).

  The number of parasitic elements (antenna elements 1 to 6) that are radiatively coupled to the feed element (antenna element 7) is controlled by controlling the reactance set of the varactor diodes 11 to 16. For example, when the number of parasitic elements that are radiatively coupled to the feed element (antenna element 7) is two, the parasitic elements that are radiatively coupled to the feed element (two antenna elements among the antenna elements 1 to 6) are used. The reactance of the loaded varactor diode is set to be relatively small, and the reactance of the varactor diode loaded to the parasitic element that is not radiatively coupled to the feeding element is set to be relatively large. The same applies to the case where the number of parasitic elements that are radiatively coupled to the feeder elements is other than two.

  When the number of parasitic elements that are radiatively coupled to the feeder elements increases, there are parasitic elements that are strongly radiatively coupled to the feeder elements, and parasitic elements that are weakly radiatively coupled to the feeder elements. When estimating the arrival direction of the incoming wave Sa1, the radiation of the feed element and the parasitic element is such that the parasitic element that is strongly radiatively coupled to the feed element rotates around the feed element at a predetermined speed <v>. The coupling is switched.

  In the above description, the varactor diodes 11 to 16 that are variable capacitance elements are loaded on the antenna elements 1 to 6 that are parasitic elements, and the reactance of the varactor diodes 11 to 16 is changed to thereby change the antenna element 7 (feeding power). The parasitic element (at least one of the antenna elements 1 to 6) that is radiatively coupled to the element) is sequentially switched. However, in the present invention, the resistance is not limited to this and instead of the varactor diodes 11 to 16. A parasitic element connected between the antenna elements 1 to 6 and the ground node and changing the resistance of the antenna elements 1 to 6 and coupled to the antenna element 7 (feeding element) may be sequentially switched.

  That is, in the present invention, a parasitic element is generally connected to the antenna element 7 (feeding element) by connecting an impedance element between the antenna elements 1 to 6 and the ground node and changing the impedance of the antenna elements 1 to 6. May be switched sequentially.

  Furthermore, in the above description, the number of parasitic elements (antenna elements 1 to 6) has been described as six. However, the present invention is not limited to this, and the number of parasitic elements is two or more. I just need it. If there are two parasitic elements, the two parasitic elements are arranged symmetrically with the feeding element as the center, and the capacitance of the two varactor diodes loaded on the parasitic elements is changed to radiate the feeding elements. This is because the parasitic element to be coupled can be rotated in a certain direction around the feeding element, so that the frequency shift due to the Doppler effect can be detected and the arrival direction of the incoming wave can be estimated by the method described above.

  Further, in the above description, the case where at least one of the antenna elements 1 to 6 and the antenna element 7 are radiatively coupled to receive a signal has been described. However, in the present invention, the array antenna 10 includes the antenna element 1. It is also possible to transmit a signal by radiatively coupling at least one of the antenna elements 6 to 6 and the antenna element 7. When the array antenna 10 transmits a signal, the reactance set of the varactor diodes 11 to 16 set when the array antenna 10 receives the signal is used as it is. That is, the array antenna 10 can transmit and receive signals by setting the reactance set of the varactor diodes 11 to 16 to the same reactance set.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention can be reduced in size and cost, is excellent in reliability and durability, and is applied to a direction-of-arrival estimation apparatus that does not require adjustment or the like by skilled techniques.

It is the schematic which shows the structure of the arrival direction estimation apparatus by embodiment of this invention. FIG. 2 is a plan layout view of antenna elements in an xy plane shown in FIG. 1. It is a top view which shows the array antenna and transmitter which are shown in FIG. It is a schematic diagram which shows the incoming wave which arrives at the array antenna shown in FIG. It is a figure for demonstrating the detection method of the frequency shift in the frequency shift detection means shown in FIG. It is a figure which shows the relationship between a phase difference and an azimuth. It is a flowchart for demonstrating the operation | movement which estimates the arrival direction of an incoming wave. FIG. 2 is a phase characteristic diagram of a beam when two antenna elements of the array antenna shown in FIG. 1 are combined. It is a figure which shows the frequency dependence of a received power spectrum at the time of combining two antenna elements of the array antenna shown in FIG. It is a figure which shows the frequency shift spectrum at the time of combining two antenna elements of the array antenna shown in FIG. It is a phase characteristic figure of the beam in the 2 element array antenna which consists of two antenna elements. It is a figure which shows the frequency dependence of the received power spectrum in the 2 element array antenna which consists of two antenna elements. It is a figure which shows the frequency shift spectrum in the 2 element array antenna which consists of two antenna elements. FIG. 5 is a phase characteristic diagram of a beam when the distance between the feeding element and the parasitic element in the array antenna shown in FIG. It is a figure which shows the frequency dependence of the received power spectrum at the time of making the space | interval of a feed element and a parasitic element in the array antenna shown in FIG. It is a figure which shows the frequency shift spectrum at the time of making the space | interval of a feed element and a parasitic element in the array antenna shown in FIG. It is a figure which shows the frequency dependence of a received power spectrum at the time of removing the frequency component of an incoming wave. It is a figure which shows the frequency shift spectrum at the time of removing the frequency component of an incoming wave. It is a figure which shows the frequency dependence of a received power spectrum at the time of using the antenna without interelement coupling. It is a figure which shows a frequency shift spectrum at the time of using the antenna without interelement coupling. It is a figure which shows the frequency dependence of a received power spectrum at the time of widening the space | interval of an antenna element in the antenna without interelement coupling. It is a figure which shows the frequency shift spectrum at the time of widening the space | interval of an antenna element in the antenna without interelement coupling. FIG. 2 is a phase characteristic diagram of a beam when all antenna elements of the array antenna shown in FIG. 1 are coupled. It is a figure which shows the frequency dependence of a received power spectrum at the time of combining all the antenna elements of the array antenna shown in FIG. It is a figure which shows the frequency shift spectrum at the time of combining all the antenna elements of the array antenna shown in FIG. It is a figure which shows the direction gain in each azimuth angle of the beam which the array antenna shown in FIG. 1 radiates | emits. FIG. 2 is a phase characteristic diagram of a beam emitted from the array antenna shown in FIG. 1. It is a figure which shows a frequency shift spectrum when the reactance set of a varactor diode is switched sequentially according to the reactance set shown in Table 4. It is a figure which shows the other frequency shift spectrum when the reactance set of a varactor diode is switched sequentially according to the reactance set shown in Table 4. It is a figure which shows the other frequency shift spectrum when the reactance set of a varactor diode is sequentially switched according to the reactance set shown in Table 4. FIG.

Explanation of symbols

  1 to 7, 61 to 67, 71 to 77 Antenna element, 8, 68, 78 Ground plate, 10, 60 array antenna, 20 coupling switching means, 21 pulse generator, 22 reactance value table, 23 variable reactance control device, 30 Amplifier, 40 Frequency shift detection means, 50 direction estimation means, 70 antenna, 100 arrival direction estimation device.

Claims (8)

An array antenna including a feeding element and n (n is a plurality) parasitic elements arranged around the feeding element;
Coupling switching means for switching a parasitic element to be coupled with the feeding element by changing at least one impedance of the n impedance elements loaded on the n parasitic elements;
When a parasitic element that is coupled to the feeder element is sequentially switched at a predetermined speed so as to rotate around the feeder element, an incoming signal received by the array antenna is received from the feeder element. A frequency shift detecting means for detecting a frequency shift spectrum of the incoming wave based on the received signal;
The frequency shift spectrum detected by the frequency shift detector detects an angle that intersects a reference line indicating that the frequency shift is zero, and estimates the detected angle as the arrival direction of the incoming wave. A direction-of-arrival estimation device comprising:   The direction estimating means detects an angle at which the frequency shift spectrum intersects the reference line when the frequency shift is switched from a positive value to a negative value, and the detected angle is used as the arrival of the incoming wave. The direction-of-arrival estimation apparatus according to claim 1, wherein the direction-of-arrival estimation apparatus estimates the direction.   The direction estimating means detects an angle at which the frequency shift spectrum intersects the reference line when the frequency shift is switched from a negative value to a positive value, and the detected angle is used as the arrival of the incoming wave. The direction-of-arrival estimation apparatus according to claim 1, wherein the direction-of-arrival estimation apparatus estimates the direction.   The coupling switching unit is configured such that all of the n parasitic elements are element-coupled to the feeder element, and a parasitic element mainly coupled to the feeder element is around the feeder element at the predetermined speed. The direction-of-arrival estimation apparatus according to any one of claims 1 to 3, wherein element coupling between the feeding element and the n parasitic elements is switched so as to rotate.   The coupling switching unit is configured such that some of the n parasitic elements are coupled to the feeder element, and the parasitic element coupled to the feeder element is disposed around the feeder element. The arrival direction estimation apparatus according to any one of claims 1 to 3, wherein element coupling between the feeding element and the n parasitic elements is switched so as to rotate at a predetermined speed. A band rejection filter that suppresses the center frequency component of the incoming wave from the received signal and outputs the received signal in which the center frequency component of the incoming wave is suppressed to the frequency shift detecting means;
The interval between the feeding element and the parasitic element is set to an interval for suppressing the center frequency component of the incoming wave,
The arrival direction estimation apparatus according to any one of claims 1 to 5, wherein the frequency shift detection unit detects the frequency shift spectrum based on a reception signal output from the band rejection filter. .   The arrival direction estimation apparatus according to any one of claims 1 to 6, wherein the n parasitic elements are arranged in a substantially circular shape around the feeder elements.   The arrival direction estimation apparatus according to any one of claims 1 to 7, wherein the impedance element is a variable capacitance element.

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